1. Field of the Invention
Disclosed herein are intrusion resistant glass laminates and composite interlayers comprising enhanced modulus polyvinyl butyral (PVB) adhesive for making glass laminates which are especially useful as intrusion resistant glazing for architectural and automotive applications.
2. Description of Related Art
Automobile and home owners, especially those who have experienced a vehicle break-in or theft or hurricane damage, are increasingly interested in intrusion resistant glazing. Glass has been identified as the weak link in the overall intrusion resistance of vehicles and buildings. For instance, some police reports estimate that broken glass is the entry route for at least 60% of unauthorized entry into passenger vehicles. There is also a belief that a 10 second delay in entry is sufficient to discourage many spontaneous thieves because the increased break-in time and additional noise call attention to the thief. In response car makers, at least, are replacing traditional tempered glass with laminated glass for side and rear glazing for enhanced security. Common automotive laminated glass can be defeated by determined thieves who use more sophisticated tools to puncture by impact and pull laminated glass out from its frame.
Attempts to improve the performance of glass laminates include modifying the stiffness and/or impact resistance of the PVB interlayer. In U.S. Pat. No. 4,814,529 Cartier et al. disclose lightly cross-linking PVB resin to selectively increase molecular weight of the PVB and the modulus of a plasticized sheet formed therefrom for use in laminated safety glass assemblies. Cartier et al. do not disclose values of modulus or construction of laminates. In U.S. Pat. No. 5,246,764 LaPorte et al. disclose laminated glazing with improved impact strength where mean break height for a dropped mass of a glass laminate increased by dispersing adhesion resistant means on the surface of PVB sheet. In U.S. Pat. No. 5,482,767 Karagiannis et al. discloses glass laminates of improved impact resistance comprising a PVB interlayer having discrete particles of crosslinked polyvinyl butyral integrally randomly dispersed throughout a matrix of PVB.
Interlayer composites of polyethylene terephthalate (PET) between layers of PVB adhesive have been used in automotive glass laminates where a thin layer of the PET, e.g. typically up to about 0.05 millimeter (2 mils) thick, has been used as a carrier for additional functional layers, e.g. of solar radiation blockers or for antennas or heat strips. See for instance, U.S. Pat. Nos. 5,208,080 and 5,979,932. U.S. Pat. No. 5,091,258 discloses composite interlayer with a 0.013 to 0.20 mm thick PET sheet coated with a multi-layer stack of infrared solar radiation reflecting materials between PVB layers. U.S. Pat. Nos. 4,017,661 and 4,768,783 disclose a composite interlayer comprising a PET sheet where a thin sheet of the PET is used as a carrier for metal layers which can be electrically resistance heated for defrosting the glass laminate. U.S. Pat. No. 4,973,511 discloses a laminated glass window construction comprising a solar control film where the glass interlayer comprised a PET sheet having on one surface at least one thin coating of metal and at least one adjacent layer of a dielectric material between layers of PVB; in the examples there is disclosed the use of a 4 mil PET film between 15 mil layers of plasticized PVB.
U.S. Pat. Nos. 5,024,895 and 5,091,258 disclose glass laminates comprising a composite interlayer where the tensile modulus for PET (at 21-15 C) is about 1010 Pa as compared with about 107 Pa for plasticized PVB of the type used in safety glazing.
An object of this invention is to provide a more intrusion resistant glass laminate, e.g. for use in security glazing applications such as architectural and automotive glazing. This is achieved by using composite interlayers comprising rigid plastic sheet and/or stiffened PVB adhesive layers providing a higher laminate stiffness.